Inflatable safety cushions, commonly known as "air bags", have been used as safety devices to protect the occupants of an automobile from injury as a result of a crash. The "air" bag is inflated with a gas very rapidly, as a collision is occurring to provide impact protection for an occupant. In the passenger side designs, the air bag deploys into the passenger compartment through an opening formed in the instrument panel while on the driver's side, a steering wheel housed compartment is used. The air bag safely absorbs the momentum of the driver or front seat passenger moving forward within the passenger compartment during a crash.
The cushion is stored uninflated in a compartment, and a closure is required to cover the deployment opening until activation. Such closure must be securely and permanently locked closed to protect against tampering with the air bag components such as to cause a malfunction. Particularly, the closure should not invite the placing of objects into the air bag compartment since these could become lethal projectiles when the air bag is deployed.
It is also desirable that the post deployment state of the closure provide a certain indication of the fact of deployment of the air bag.
At the same time, the closure must operate very reliably to open when needed, almost instantaneously and in such a way as to not interfere with proper deployment of the air bag. Thus only smooth contours should be contacted by the bag during deployment, avoiding the presence of sharp projections.
Since deployment of the air bag must be complete within only a few milleseconds, a typical requirement is that the closure must be open within 3 milliseconds, when operated by the pressure exerted by the air bag as it inflates, and thus a light weight structure is imperative.
The system must operate very reliably over a wide range of temperatures and other environmental conditions. For example, a 40.degree. C. low and 105.degree. C. high temperature standards have been proposed corresponding to commonly used design criteria applied to other automotive components, which temperature standards have not heretofore been met for air bag deployment opening closures.
For reliability and cost considerations, a simple design must be employed, utilizing a minimum number of parts. It is important that hazardous fragments from the closure itself should not be directed into the passenger compartment upon deployment.
It is thus an object of the present invention to provide a simple, lightweight, and tamper resistant closure for an air bag deployment opening which does not interfere with proper deployment of the air bag.
It is another object to provide such closure which operates reliably over a wide range of temperatures.
A further object is to provide such a closure in which the pressure of the inflating air bag is exerted for optimal effectiveness to ensure reliable and consistent opening of the closure.
Yet another object is to provide such a closure which involves a minimum number of moving parts, and which does not result in hazardous debris being showered into the passenger compartment upon opening, and which provides a certain indication of the fact of air bag deployment.